The present invention relates to an eco-run control device and an eco-run control method for controlling a vehicle to perform eco-run.
In recent years, a vehicle performs eco-driving (hereinafter, also referred to as eco-run) including automatic stopping of the engine (for example, idling stop) in order to improve the gas mileage of the vehicle and to suppress exhaust gas emissions.
In this specification, it is assumed that “eco” means at least one of “economy” and “ecology”. Economy means fuel savings (reduction in fuel consumption) by suppressing fuel consumption. Ecology means suppressing fossil fuel consumption or suppressing the generation or emissions of harmful substances or carbon dioxide caused by combustion of fossil fuels.
A vehicle which performs eco-run includes a detector which detects a state of the vehicle, and a control device which performs eco-run control on the basis of the state detected by the detector. The eco-run control refers to a control of automatically stopping the engine when it is determined that the predetermined stop conditions are satisfied on the basis of the vehicle state detected by the detector and of automatically starting the engine when it is determined that the predetermined restart conditions are satisfied on the basis of the vehicle state detected by the detector.
In order to prevent being unable to restart the engine after stopping the engine by eco-run control, Patent Document 1 discloses a failure detection method for detecting the failure of a starter driving circuit which restarts the engine.
In this failure detection method, failure of the starter driving circuit is detected before automatically stopping the engine by eco-run control by setting the failure detection timing of the starter driving circuit as a time when the engine stop conditions are satisfied. Moreover, in this failure detection method, stopping of the engine by eco-run control is prohibited by prohibiting the execution of the eco-run control when the failure is detected.
Patent Document 2 discloses a control device which performs the eco-run control and which is capable of preventing erroneous detection in a failure test of a starter driving circuit.
This control device executes mask processing of masking the detected failure for a failure test result when performing a failure test for the starter driving circuit, which restarts the engine, in a predetermined period for which a voltage drop caused by a restart occurs after restarting the engine.
Patent Document 3 discloses a control apparatus having an automatic engine stop function and an abnormal diagnosis function. This control device can stop an engine automatically when a predetermined automatic stop conditions are satisfied and can execute a self-abnormal diagnosis. In order to frequently execute the abnormal diagnosis, the control device prohibits execution of the automatic engine stop if the control device has not yet executed the abnormal diagnosis to be executed, even when the automatic stop conditions are satisfied.    Patent Document 1: JP-A-2006-322332    Patent Document 2: JP-A-2007-46546    Patent Document 3: JP-A-2008-151041
In the failure diagnosis method disclosed in Patent Document 1, however, there is a problem that a microcomputer erroneously detected the failure of a starter driving circuit when the voltage state of the microcomputer is different from the voltage state of the starter driving circuit. Specifically, there is a problem that the microcomputer erroneously detects the failure of the starter driving circuit when a voltage applied to the starter driving circuit drops in a period for which the microcomputer tests the failure of the starter driving circuit.
As a specific example, as shown in FIG. 2A, the case where a microcomputer 920 and a starter driving circuit 910 operate using the same +B power source and the microcomputer 920 can operate using a lower voltage than for the starter driving circuit 910 will be described. In this case, there is a problem that if the voltage of the +B power source drops so that the starter driving circuit 910 can not operate although the microcomputer 920 could operate, the microcomputer 920 erroneously detects that the starter driving circuit 910 fails even though the starter driving circuit 910 does not actually fail.
Similarly, as a specific example, if only the voltage applied to the starter driving circuit 910 drops when the microcomputer 920 and the starter driving circuit 910 operate using different power sources as shown in FIG. 2B, there is a problem that the microcomputer 920 erroneously detects the failure of the starter driving circuit 910.
Moreover, in the control device disclosed in Patent Document 2 for solving these problems, the failure is masked from the test result of the starter driving circuit 910 over a predetermined time after restarting the engine. For this reason, in the control device disclosed in Patent Document 2, there is a problem that the execution of eco-run control is permitted even when the failure actually occurred.
Patent Document 3 takes exhaust gas sensors, a catalyst, a fuel system and an ignition system for example of components or systems to be diagnosed. However, Patent Document 3 does not discloses testing a starter driving circuit. In addition, there is no mention of erroneous failure detection due to the voltage reduction.